1800 The Act of Union 1800 is passed in which merges the Kingdom of Great Britain and the Kingdom of Ireland into the United Kingdom of Great Britain and Ireland.
1801 The legislative union of Kingdom of Great Britain and Kingdom of Ireland is completed to form the United Kingdom of Great Britain and Ireland.
1803 The Convention of Artlenburg leads to the French occupation of Hanover (which had been ruled by the British king).
1812 War of 1812: American frigate ''USS Constitution'' defeats the British frigate ''HMS Guerriere'' off the coast of Nova Scotia, Canada earning her nickname "Old Ironsides".
1813 War of 1812: three weeks of British raids on Fort Schlosser, Black Rock and Plattsburgh, New York begin.
1814 Washington, D.C. is burned and White House is destroyed by British forces during the War of 1812.
1815 Signing of the Kandyan Convention treaty by British invaders and the King of Sri Lanka.
1820 Cato Street Conspiracy: A plot to murder all the British cabinet ministers is exposed.
1830 Charles Grey, (2nd Earl Grey), became Prime Minister of the United Kingdom.
1831 William IV and Adelaide of Saxe-Meiningen are crowned King and Queen of the United Kingdom of Great Britain and Ireland.
1833 The United Kingdom claims sovereignty over the Falkland Islands.
1837 Queen Victoria succeeds to the British throne.
1840 The Penny Black postage stamp becomes valid for use in the United Kingdom of Great Britain and Ireland.
1854 Crimean War: France and Britain declare war on Russia.
1856 The Iranian city of Bushehr surrenders to occupying British forces.
1862 The United States and Britain agree to suppress the slave trade.
1867 Singapore becomes a British crown colony.
1873 The British steamer {{RMS|Atlantic}} sinks off Nova Scotia, killing 547.
1878 The British frigate {{HMS|Eurydice|1843|6}} sinks, killing more than 300.
1879 Anglo-Zulu War: Battle of Kambula: British forces defeat 20,000 Zulus.
1879 Cetshwayo, last king of the Zulus, is captured by the British.
1882 Britain's first electric trams run in east London.
1884 The United Kingdom ends its policy of penal transportation to New South Wales in Australia.
1895 The National Trust is founded in the United Kingdom.
1900 Second Boer War: In South Africa, 20,000 British troops invade the Orange Free State.
1902 Edward VII and Alexandra of Denmark are crowned King and Queen of the United Kingdom of Great Britain and Ireland.
1904 The French Third Republic and the United Kingdom of Great Britain and Ireland sign the ''Entente cordiale''.
1911 George V and Mary of Teck are crowned King and Queen of the United Kingdom of Great Britain and Ireland.
1914 World War I: the German colony of Togoland is invaded by French and British forces, who take it after 5 days.
1916 Easter Rebellion: Martial law in Ireland is lifted and the rebellion is officially over with the surrender of Irish nationalists to British authorities in Dublin.
1916 The Irish Nationalist and British diplomat Sir Roger Casement is sentenced to death for his part in the Easter Rising.